Explicitly inform PacketRouter which RTP-RTCP modules are REMB-candidates

webrtc/modules/pacing/packet_router.h

Index: webrtc/modules/pacing/packet_router.h
diff --git a/webrtc/modules/pacing/packet_router.h b/webrtc/modules/pacing/packet_router.h
index 12d726a2aacdabbfea8e920fd0c7f250a287ceb9..3d98d1028b21ca8e1cd6c2007fbd9efd071e8f1d 100644
--- a/webrtc/modules/pacing/packet_router.h
+++ b/webrtc/modules/pacing/packet_router.h
@@ -44,15 +44,16 @@ class PacketRouter : public PacedSender::PacketSender,
 
   // TODO(nisse): Delete, as soon as downstream app is updated.
   RTC_DEPRECATED void AddRtpModule(RtpRtcp* rtp_module) {
-    AddReceiveRtpModule(rtp_module);
+    constexpr bool remb_candidate = true;  // Default to old behavior.
+    AddReceiveRtpModule(rtp_module, remb_candidate);
   }
   RTC_DEPRECATED void RemoveRtpModule(RtpRtcp* rtp_module) {
     RemoveReceiveRtpModule(rtp_module);
   }
-  void AddSendRtpModule(RtpRtcp* rtp_module);
+  void AddSendRtpModule(RtpRtcp* rtp_module, bool remb_candidate);

[danilchap, 2017/07/19 12:47:20]

overload to make the change backward compatible.
(but feel free to mark old signature RTC_DEPRECATED to discourage it)

Though it might be better to add SupportsRemb / SupportsTransportCC to the
RtpRtcp interface itself to avoid introducing odd parameters.

[eladalon, 2017/07/27 15:57:26]

Done.
(For posterity - keeping remb_candidate because the class currently manages REMB
transmission.)

   void RemoveSendRtpModule(RtpRtcp* rtp_module);
 
-  void AddReceiveRtpModule(RtpRtcp* rtp_module);
+  void AddReceiveRtpModule(RtpRtcp* rtp_module, bool remb_candidate);
   void RemoveReceiveRtpModule(RtpRtcp* rtp_module);
 
   // Implements PacedSender::Callback.
@@ -84,11 +85,19 @@ class PacketRouter : public PacedSender::PacketSender,
   virtual bool SendTransportFeedback(rtcp::TransportFeedback* packet);
 
  private:
+  void AddRembModuleCandidate(RtpRtcp* candidate_module, bool sender)
+      EXCLUSIVE_LOCKS_REQUIRED(modules_crit_);
+  void MaybeRemoveRembModuleCandidate(RtpRtcp* candidate_module, bool sender)
+      EXCLUSIVE_LOCKS_REQUIRED(modules_crit_);
+  void DetermineActiveRembModule() EXCLUSIVE_LOCKS_REQUIRED(modules_crit_);
+
   rtc::RaceChecker pacer_race_;
   rtc::CriticalSection modules_crit_;
   std::list<RtpRtcp*> rtp_send_modules_ GUARDED_BY(modules_crit_);
   std::vector<RtpRtcp*> rtp_receive_modules_ GUARDED_BY(modules_crit_);
 
+  // TODO(eladalon): remb_crit_ only ever held from one function, and it's not
+  // clear if that function can actually be caleld from more than one thread.
   rtc::CriticalSection remb_crit_;
   // The last time a REMB was sent.
   int64_t last_remb_time_ms_ GUARDED_BY(remb_crit_);
@@ -96,6 +105,12 @@ class PacketRouter : public PacedSender::PacketSender,
   // The last bitrate update.
   uint32_t bitrate_bps_ GUARDED_BY(remb_crit_);
 
+  // Candidates for the REMB module can be RTP sender/receiver modules, with
+  // the sender modules taking precedence.
+  std::vector<RtpRtcp*> sender_remb_candidates_ GUARDED_BY(modules_crit_);
+  std::vector<RtpRtcp*> receiver_remb_candidates_ GUARDED_BY(modules_crit_);
+  RtpRtcp* active_remb_module_ GUARDED_BY(modules_crit_);
+
   volatile int transport_seq_;
 
   RTC_DISALLOW_COPY_AND_ASSIGN(PacketRouter);